Power plants – Combustion products used as motive fluid
Reexamination Certificate
1999-12-03
2001-01-30
Casaregola, Louis J. (Department: 3746)
Power plants
Combustion products used as motive fluid
Reexamination Certificate
active
06178736
ABSTRACT:
TECHNICAL FIELD
This invention pertains to starter systems and controllers for turbine aircraft engines and to methods of starting turbine aircraft engines.
BACKGROUND OF THE INVENTION
Turbine aircraft engines are started by beginning engine rotation, introducing fuel at a proper time to achieve ignition, and accelerating the engine to a self-sustaining ground idle condition. The whole process is commonly known as the start cycle. An electric starter or starter/generator is used to initially rotate the engine and accelerate it to the point where it runs under its own power.
During the time between initial engine rotation and fuel ignition, the engine does not experience a meaningful amount of temperature-induced stress. However, at the point of ignition through acceleration to ground idle, the engine does experience a meaningful amount of temperature-induced stress. In fact, the stress experienced by the engine during this time is greater than the stress experienced during takeoff and flight. Hence, it is desirable to reduce the time exposure within the engine start cycle between ignition and ground idle. It is also desirable to reduce the temperature which is seen by the engine during this time.
One solution to reducing the engine's start cycle duration might be to accelerate the engine as rapidly as possible through the start cycle beginning with initiation of the start cycle. This however poses some problems which are equally if not more stressful on the engine. One might, for example, initially supply the starter with all of the power necessary for the starter to take the engine through the entire start cycle. Doing so does not meaningfully improve the quality of the start and can stress electrical components including the starter, which are susceptible to heat damage caused through the dissipation of excess current and engine torque. Over a period of time, such electrical and engine components can wear out prematurely and require replacement. It would be ideal to have an engine start system which is sensitive to the engine start cycle and can react and manage the cycle for efficient and low-stress engine starts.
This invention arose out of concerns associated with providing a starter system for a turbine aircraft engine which monitors and manages the start cycle to produce a more efficient start with less stress to the engine.
SUMMARY OF THE INVENTION
Turbine aircraft engine starter systems and controllers for use therewith, and methods of starting turbine aircraft engines are described. A starter is operably connected with an aircraft engine and configured to initiate an engine start cycle which includes engine rotation and a fuel ignition point. In one aspect, a power source is connected with the starter and is configured to provide power thereto in accordance with at least first and second settings which apply different magnitudes of voltage to the starter. The first setting initiates the engine start cycle and the second setting accelerates the engine through the start cycle after the fuel ignition point. A controller is operably connected with the starter and the power source and is configured to monitor the engine start cycle and responsive to a controller-determinable time during the engine start cycle changes the first setting to the second setting. In a preferred implementation, the power source comprises a pair of batteries which are permanently connected in series.
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Rolls Royce Ltd.The Jet Engine; Jul., 1969. pp. 123-125.
Casaregola Louis J.
Lamar Technologies Corporation
Wells, St. John, Roberts Gregory & Matkin P.S.
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